The present invention relates to a device for clamping one or more pieces of fabric in position to be embroidered by an automatic embroidery machine. Such machines include electronic circuitry which controls the motion of a traveller, which is mounted for movement along two perpendicular axes. The traveller is connected to the clamping device which is in turn slidably supported on the machine work table so that the clamping device can be moved to any desired position with respect to the sewing mechanism of the machine. The invention is especially adapted for use with multihead machines wherein a plurality of pieces of fabric are clamped in position relative to a plurality of needles.
Embroidery hoops such as shown in U.S. Pat. No. 3,818,620 have been employed in the prior art to support individual pieces of fabric to be embroidered. These hoops are supported by a spider adapted to support a plurality of hoops. Some spiders now in use are made of plywood having holes therein which receive and support the hoops. Such spiders have a number of problems. They are affected by temperature and humidity, and warpage is very common. They are also heavy and induce considerable wear on the associated embroidery machines.
Wooden spiders do not firmly support the hoops and the clamped fabric in position. As a result, the hoops are sometimes vibrated out of the spider. Furthermore, the number of irregulars as well as thread breakage from hoop bounce occurring with the use of wooden spiders is excessive. Accordingly, considerable maintenance is required which results in loss of productivity due to down time.
A clamping device as shown in U.S. Pat. No. 3,664,288 has also been proposed for use with embroidery machines. However, this type of device suffers from the disadvantages of being bulky, heavy and expensive in construction.